wT3 matrjiidiiPt Indian Standard CRITERIA FOR HYDRAULICDESIGNOFSURGETANKS PART 3 SPECIAL SURGE TANKS ' UDC 627'846: 624'04 @ BIS 1991 BUREAU MANAK OF BHAVAN, INDIAN STANDARDS ZAFAR MARG 9 BAHADUR SHAH NEW DELHI 110002 JunuuYy 1991 Price Group 3 Water Conductor Systems Sectional Committee, RVD 14 FOREWORD This Indian Standard (Part 3 ) was adopted by the Bureau of Indian Standards on 27 March 1990, after the draft finalized by the Water Conductor Systems Sectional Committee had been approved by the River Valley Projects Division Council. Part 3 deals with the surge tank which absorbs the water hammer or elastic shock waves coming from the pressure pipe line or tunnel on closure or opening of the valve or turbine gates and also to supply/store additional water during load acceptance/rejection during load demand/rejection until the conduit velocity has accelerated/decelerated to the new steady state value. Surges or mass oscillations occur in the surge tanks, the hydraulic design of which is so done as to keep the surges within reasonable limits. Special surge tanks may be defined as simple or restricted orifice type surge tanks which have additional features like expansion galleries ( chambers ), spilling arrangements, etc. Air cushion Surge tanks with upper and/or lower expansion surge chambers also fall under this category. galleries are covered in this standard ( see Fig. 1 ). The expansion galleries ( chambers ) are provided under the following conditions: a) When the computed maximum and minimum surge levels are found to be higher/lower than the maximum and minimum levels of the surges fixed in accordance with IS 7396 ( Part 1 ) : 1985 `Criteria for hydraulic design of surge tanks: Part 1 Simple, restricted orifice and differential surge tanks', IS 7396 ( Part 2 ) : 1985 `Criteria for hydraulic design of surge tanks: Part 2 Tail race surge tanks' and IS 7396 (Part 4) : 1983 `Criteria for hydraulic design of surge tanks: Part 4 Multiple surge tanks', based on the turbine characteristic ( see Fig. 2 ). b) Many a times in case of conventional surge tanks, long approach tunnels are required to be constructed. Sometimes for economy a portion of the approach tunnel is utilized as an expansion gallery and the upper portion of the gallery serves as an air vent, if the maximum upsurge remains below the soffit at the mouth of the approach tunnel ( see Fig. 3 ). This standard has been prepared in parts. Other parts of this standard orifice and differential are as follows: surge tanks (just revision ) IS 7396 ( Part 1 ) : 1985 IS 7396 ( Part 2 ) : 1985 IS 7396 ( Part 4) : 1983 Simple, restricted Tail race surge tanks (first revision ) Multiple surge tanks IS 7396 ( Part 3) : 1990 Indian Standard HYDRAULIC PART 1 SCOPE 1.1 This standard (Part 3 ) lays down the criteria for hydraulic design of surge tanks with expansion galleries/chambers. 2 REFERENCES CRITERIA FOR DESIGN OF SURGE TANKS 3 SPECIAL SURGE TANKS 1985. Draw the line XT in Fig. 4 at the point A of Fig. 2. Draw the modified QLT Curve as AX' 2" CD ( Fig. 5 ). Find out the volume as below: Volume r= 2 QT At (A, portion in Fig. 5 ) where 5 z=~ elevation T in metres, and in m"/sec. = area of shaded 2.1 The Indian Standard 1985 is necessary adjunct 3 TERMINOLOGY (Part to this standard. IS 7396 1) : time in seconds, 3.1 For "PPlY* the purpose of definitions given in IS 7396 this (Part standard the 1 ) : 1985 shall QLT= discharge in tunnel 4 DATA 4.1 The data required for the design of special surge tanks with upper/lower expansion gallery/ chamber shall be in accordance with IS 7396 (Part 1) : 1985. 4.2 At the time of design of surge system, the designer should ascertain the geological features around the location of the surge tank to the extent of 500 m. 5 DESIGN Keeping factor of safety as 2, the volume of expansion gallery is fixed as twice the volume calculated by the above formula for the preliminary analysis. 6.2 After finding ( see Fig. 1A ) of ( chambers ) are analysis (preferably made to check the water level in the the fixed level A as out the volume, dimensions the expansion galleries tentatively fixed and the with the computer) is fixed dimensions so that the surge tank does not exceed shown in Fig. 2. 5.1 Design Conditions 7 TENTATIVE VOLUME OF LOWER EXPANSION GALLERIES/CHAMBERS 5.1.1 The maximum and minimum water levels ( A & B) in the surge tank shall be determined depending upon the turbine characteristics ( see Fig. 2 ) and the percentage to be allowed over the design head within the permissible safety of the machine. 5.1.2 The maximum and minimum water levels in the surge tanks ( c 8~D) shall be found out in accordance with 5.1.1, 5.1.1.1 and 5.1.1.2 of IS 7396 (Part 1 ) : 1985. If these water levels work out to be higher/lower than worked out as under 5.1.1 of this standard, the necessity of upper expansion gallery or lower expansion gallery would arise. 6 TENTATiVE 7.1 The procedure be followed. 8 ANALYSIS given in 6.1 and 6.2 shall 8.1 Upper Expansion Gallery gallery is the height under 5.1.1 When the necessity of expansion established the difference between of maximum water level calculated and 5.1.2 is found out. 8.1.1 Shape gallery should The shape of upper expansion preferably be D-shaped. 8.1.2 Size EXPANSION 6.1 Draw VOLUME OF UPPER GALLERIES/CHAMBERS the two curves 5 vs I and QT vs r as shown in Fig. 4 and 5 from the values obtained from 5.1.1, 5.1.1.1, 5.1.1.2 of IS 7396 (Part I ) : 1 Area of the expansion gallery/galleries should be determined on the basis of discharge and generally height should be more than the width of the gallery. IS 7396 ( Part 3 ) : 1990 8.1.3 Layout of Upper Galleries Typical and 3. layout of galleries is shown in Fig. 1 preferably 8.2.2 Size The area of lower expansion gallery/galleries shall be in accordance with 8.1.2. 8.2.3 Slope Slopes shall not be flatter shown in Fig. 1. 8.2.4 Layout of Lower Galleries Typical and 3. layout of galleries is shown in Fig. 1 than 1 in 150 as be D-shaped. The gallery/galleries may be connected with surge tank with its roof level generally at/below level determined in water the maximum accordance with 5.1.1. 8.1.4 Slope Slope of the gallery should not be less than 1 in 150 as shown in Fig. 1 in order to empty out the gallery efficiently. 8.2 Lower Expansion 8.2.1 Shape The shape of lower expansion gallery should Gallery The gallery/galleries may be connected with the surge tank with its bottom level generally at/ above the minimum water level determined in accordance with 5.1.1. IS 7396 ( Part 3 1 : 1990 MAXIMUM WATER LEVEL ----c AIR VELT UPPER EXPANSION GALLERY SLOPE 1 IN lso . LOWER EXPANSION GALLERY/ -_--_ SLOPE 1 IN 150 __-_ m--v -AT -Q T MINIMUM WATER LEVEL A ,,= AREA OF TUNNEL As = AREA OF SURGE TANK 1A MAX WATER LEVEL UPPER EXPANS_ION GALLERY SLOPE 1 IN 150- SLOPE 1 IN 150 _ HiN WATER LEVEL> ---z ---_' J SLOPE 1 IN 150 LOWER EXPANSION GALLERY 1B FIG. 1 TYPICAL TYPES OF SURGE TANK WITH EXPANSION GALLERY 3 IS 7396(Part3):1!HO SURGE TANRz 4 ._- 4 RESERVOIR --_ MWL _- P-. G c.7---------e-v -- -52 VM --_ X LwL.Y-. -:---------- .-_s ---_ . X v` WI --- -_- 1 r NOTES A = Maximum B = Minimum C & D = Maximum water level as per the turbine water level as per the turbine & minimum water level characteristics characteristics condition ( scc 5.1.2 ) E & F = Minimum & maximum water level at the draw-down G & H = Maximum & minimum water level in the reservoir FIG. 2 SURGE TANK ACCORDING TO TURBINE CHARACTERISTICS WHlU?4 WATER LEVEL -_---__ ----__ A_^ -\J 1 SL4M'E 1 IN.150 b 5 ffIN WATER LEVEL -----_ a--- RETAINING WAU. L EXPANSION GALLERY APPROACH TuwtlEL As = AREA OF SURGE TAM AT -AREAOFTUNNF& FIG. 3 SURGE TANK WITH PART OF APPROACH 4 TUNNEL AS EXPANSION GALLERY IS 7396 ( Part 3 ) : 1990 60 LEVEL A OF Fig.2 44 20 2 0 t -20 -40 -60 -80 FULL RESFRVOIR LEVEL -T SCALE -VS: HS: 1 cm = 20 seconds 1 cm = 6.1 m l-h. 4 ELEVATION AND TIME RELATIONSHIP SCALE HS: 1 cm = 20 secqnds 28 . 34r&sec) vs:1ca= FIG. 5 DISCHARGE AND TIME RELATIONSHIP 5 Standard Mark The use of the Standard Mark is governed by the provisions of the Br~eau Q/" Ztuliurl Stmtlurtls Act, lY86 and the Rules and Regulations made thereunder. The Standard Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well defined system of inspection, testing and quality control which is devised and supervised by RIS and operated by the producer. 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